From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Sun, 31 Mar 2019 15:33:11 +0000 (+0200)
Subject: Check return value of buf_move_to_buf for error.
X-Git-Tag: tor-0.4.0.4-rc~6^2^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a628e36024c4db6e5b178abe3a0b2784c0ab00ec;p=thirdparty%2Ftor.git

Check return value of buf_move_to_buf for error.

If the concatenation of connection buffer and the buffer of linked
connection exceeds INT_MAX bytes, then buf_move_to_buf returns -1 as an
error value.

This value is currently casted to size_t (variable n_read) and will
erroneously lead to an increasement of variable "max_to_read".

This in turn can be used to call connection_buf_read_from_socket to
store more data inside the buffer than expected and clogging the
connection buffer.

If the linked connection buffer was able to overflow INT_MAX, the call
of buf_move_to_buf would have previously internally triggered an integer
overflow, corrupting the state of the connection buffer.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/src/or/connection.c b/src/or/connection.c
index 0a2a635096..f18ef74536 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -3561,6 +3561,10 @@ connection_buf_read_from_socket(connection_t *conn, ssize_t *max_to_read,
     if (conn->linked_conn) {
       result = buf_move_to_buf(conn->inbuf, conn->linked_conn->outbuf,
                                &conn->linked_conn->outbuf_flushlen);
+      if (BUG(result<0)) {
+        log_warn(LD_BUG, "reading from linked connection buffer failed.");
+        return -1;
+      }
     } else {
       result = 0;
     }